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Old 06-30-2011, 08:35 AM   #16
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Originally Posted by bertrandsv87 View Post
ecomet , I don't know where you got that info , but I am afraid some of it is incorrect!!! There is no way a 25.5=27t ok! To the guy that started the thread, you need to do your homework before you call the priceless info we willingly give you non-answers!!! If you leave this hobby for two months, you will be left behind, let alone two years!!! DO YOUR HOMEWORK!!!!!!!!!!!!!
asking you guys questions is part of that homework. Isn't that what forums are for? ask a question, get an answer?
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Old 06-30-2011, 09:13 AM   #17
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Originally Posted by Sabin View Post
asking you guys questions is part of that homework. Isn't that what forums are for? ask a question, get an answer?
Questions all well and good but dont dis regaurd what ppl are helping you with and giving you your answers for your home work....
Just because you dont think thats the answer you were expecting or it doesnt tell you exactly what you were wanting ask more questions and dont start putting other ppl down....
Thats right it is a forum and the only way to learn is to read read and read all different opinions and take what you want out of it as there is no need to tell ppl that its not good enough when your the one learning..
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Old 06-30-2011, 09:35 AM   #18
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Originally Posted by Sabin View Post
asking you guys questions is part of that homework. Isn't that what forums are for? ask a question, get an answer?
Then don't get mad at the answers you get.


As part of your "homework," it's your job to interpolate what you can from the information given to you. You can't expect to get a simple, succinct answer that would cover the advances in technology over the "good couple [of] years" that you've been away from the hobby.

For example, if your initial questions were
Quote:
"Does a 21.5 brushless motor have approximately the same speed as a 27T brushed motor?"
and
Quote:
"Does a 17.5t brushless motor compare to a 19T motor in terms of speed?"
then mooby64's basic scale of
Quote:
"In order slowest to fastest.......25.5, sliver can, 21.5, 27t brushed, 17.5, 16.5, 15.5 ....etc."
should have given you a basic answer since you were just looking for approximate and comparative equivalents, not exact equivalents. You could couple mooby64's answer with that of bertrandsv87, who said
Quote:
"I only run brushed 27t against 17.5 blinky and it really comes down to the driver!!! 19t brushed is also faster than 13.5 brushless with no esc timing"
to realize that, "In a situation where no boost or advanced timing is applied via the ESC, a 17.5T brushless motor is approximately as fast as a good 27T brushed motor, but it does not compare to a 19T brushed motor since a 19T brushed motor is faster than a 13.5T brushless motor, and 13.5T motors are apparently faster than 17.5T motors."

If you want some more homework, do the math :
If A = (a 19T brushed motor), B = (a 13.5T brushless motor), and C = (a 17.5T brushless motor)...and if A > B, and B > C, then A > C.

My own experience comports with that of bertrandsv87's statement, because in the past I have run an old CO27 (27T brushed motor) against 17.5T brushless motors in a no-timing TC class and have been able to keep pace with the brushless guys. I've also run my Checkpoint Money (19T brushed motor) against my Novak SS13.5T brushless motor (also no-timing on the ESC) in my old stadium truck and definitely had more speed with the Money motor. However, I currently have a 17.5T brushless in my short course truck with the latest SpeedPassion stock boost timing software, and it sure feels like it could give that 19T stadium truck (which I don't have anymore) a run for its money (pun intended ).

As JR007 said, even brushless motors from a few years back are not as powerful as the brushless motors of today...and that's not even taking into account the advances in ESC technology. When you couple that with the fact that brushed technology has all but become stagnant since brushless has become the prevalent choice for powerplants, it's somewhat difficult to determine a baseline exact comparison. Even governing bodies such as ROAR have had to modify motor designations for some of the classes because of increases in speed due to technological advances (i.e., "stock" changing from 13.5 to 17.5 to 21.5 to 25.5, etc.).
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Old 06-30-2011, 10:09 AM   #19
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Well said encore75 !!!!
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Old 06-30-2011, 10:24 AM   #20
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Part of the problem I see (having been in when AM/brushed nicd batts were "it") if we are asking to compare motor to motor. Look at it like this:

I have several older BRUSHED cars I am moving to BL. I more than likely am not a racer, but a basher. I want to put something in, not play with all the settings, and have an equivalent speed/power setup. A touch faster probably isnt too bad but an order of magnitude is.

For instance. I have a TC4 that I moved from a speedgems (can't remember exactly but 17t sounds about right) to a MM/5700. While I did swap the speed control out I wanted something that was about the same power wise (again, a little more power is ok but lets not get crazy).

Yes I need to adjust some gearing but a simple out-of-the-box-fresh conversion should be possible.

This kv vs turn business is nuts too and forgive me for thinking a 13t BRUSHED motor should be pretty darn close to a motor that has a sticker on the side that says "13.5t"


Thanks to encore and more importantly COMET as that was what both I and the op were looking for.
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Old 06-30-2011, 12:20 PM   #21
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Yeah, but unfortunately I think the chart that was put up was completely wrong. Just because it's on a chart, doesn't make it right.
There is no way you can compare those and get an accurate answer.
If you are just upgrading old gear, again, you should ask what motor to start with to get "similar" performance to the motor you had. There will be somone on here who ran motors like yours.
It's a case-by-case basis as there are so many different motors all with differences in performance. Even back in the day, 19T motors could have double the power between different types!
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Old 06-30-2011, 02:43 PM   #22
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Exclamation It's just a reference!

The chart I posted is an very early reference when brushless motors first started to appear. It was quoted from another site, which I forgot the name.

I repeat, it is just a reference since the OP just want to get an idea. And of course we all know the current motors are much different from before. There was no sensored motor back then.

The brushless motor only has kv value which is comparable to brushed rpm (total rpm / 7.2V in the old days). Nowadays we use 7.4V lipo so the graph is not going to be very accurate.

Even different motors are built differently, and each with different factory timing. For example, a 17.5 with 40 degrees timing would be equivalent to a 13.5 with 0 degree timing and so on. So direct comparison is not going to be possible.

Instead of trying to bash me for wrong info, I am simply providing a ball-park, which I think the OP is looking for. There is no ABSOLUTELY ACCURATE comparison whatsoever.

Lastly, just use it as a ball-park reference.
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Old 06-30-2011, 03:14 PM   #23
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Here is a real-world scenario that might help. Again, this is just my impressions

I am running in a GT Touring Car series this summer where we have a motor limit of 17.5 non-boosted brushless or 27t brushed.

I am the only guy out of 6 running brushed motors. I am running a Putnam Propulsions dyno tuned "Excessive Force" Epic based motor, with a crappy XL-5 brushed ESC (I think it's only 60amp max)

We just put together a large oval race in a parking lot, where most of us were geared pretty close to the same. (around 6.00 fdr)

My car, running the 27t brushed motor, was no slower than any of the other cars once they got up to speed down the main straight, but seemed to lack a little bit of the accelleration out of the corners that the other cars had when geared that tall. Also, my temperatures were close to what they had as well.

my 10 fastest laps were all under 7 seconds, where most of the other guys only pulled a few sub-7 second laps. (we were running 5 lap qualifiers, 20 lap heats, and a 30 lap main.)

IMHO a GOOD 27t is equivelent in SPEED to an AVERAGE 17.5 non-boosted, but lacks a little bit of low end punch/accelleration/torque....
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Old 06-30-2011, 06:25 PM   #24
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Quote:
Originally Posted by eComet View Post
The chart I posted is an very early reference when brushless motors first started to appear. It was quoted from another site, which I forgot the name.

I repeat, it is just a reference since the OP just want to get an idea. And of course we all know the current motors are much different from before. There was no sensored motor back then.

The brushless motor only has kv value which is comparable to brushed rpm (total rpm / 7.2V in the old days). Nowadays we use 7.4V lipo so the graph is not going to be very accurate.

Even different motors are built differently, and each with different factory timing. For example, a 17.5 with 40 degrees timing would be equivalent to a 13.5 with 0 degree timing and so on. So direct comparison is not going to be possible.

Instead of trying to bash me for wrong info, I am simply providing a ball-park, which I think the OP is looking for. There is no ABSOLUTELY ACCURATE comparison whatsoever.

Lastly, just use it as a ball-park reference.
Again, thank you very much for the table. Appreciate it immensely and it gives me a great starting point to continue down the road that I'm going on.

If there was a kudos function, i'd click it for that post.

Quote:
Questions all well and good but dont dis regaurd what ppl are helping you with and giving you your answers for your home work....
True enough, but they weren't needed at that point in time. Later on, sure. go crazy. but not when someone is trying to find a general reference.

Just try to keep in mind that information overload is a bad thing when starting out.
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Old 07-03-2011, 11:43 AM   #25
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GM rates their dr speed 2x12turn brushed to be 220watts.

At the same time most 10.5t brushless motors seems to be rated around 250- 300watts. 10T brushed = 10.5T brushless perhaps.

http://forum.radiostyrt.no/vb/showth...tor-registeret
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